arp

NAME

       arp - manipulate the system ARP cache

SYNOPSIS

       arp [-v] [-t type] -a [hostname]
       arp [-v] -d hostname ...
       arp  [-v]  [-t  type]  -s hostname hw_addr [temp] [netmask
       aa.bb.cc.dd] [pub]
       arp [-v] -f filename

DESCRIPTION

       Arp manipulates the kernel's ARP cache  in  various  ways.
       The  primary options are clearing an address mapping entry
       and manually setting up one.  For debugging purposes,  the
       arp  program also allows a complete dump of the ARP cache.

OPTIONS

       -v     Tell the user what is going on by being verbose.

       -t type
              When  setting  or  reading  the  ARP  cache,   this
              optional parameter tells arp which class of entries
              it should check for.  The  default  value  of  this
              parameter  is  ether  (i.e.  hardware code 0x01 for
              IEEE 802.3 10Mbps Ethernet ARCnet (arcnet) , PROnet
              (pronet) and AX.25 (ax25)

       -a [hostname]
              Shows  the  entries of the specified hosts.  If the
              hostname parameter is not used, all entries will be
              displayed.

       -d hostname
              Remove  any entry for the specified host.  This can
              be used if the indicated host is brought down,  for
              example.

       -s hostname hw_addr
              Manually  create  an  ARP address mapping entry for
              host hostname with hardware address set to  hw_addr
              class, but for most classes one can assume that the
              usual presentation can be used.  For  the  Ethernet
              class, this is 6 bytes in hexadecimal, separated by
              colons. When adding  proxy  arp  entries  (that  is
              those  with the [pub]lish flag set a netmask may be
              specified to proxy arp for  entire  subnets.  Proxy
              arp  for routing entire networks is not a good pro-
              tocol, but its sometimes useful so supported.

       -f filename
              Similar to  the  -s  option,  only  this  time  the
              address  info  is  taken from file filename set up.
              The name of the data file is very often /etc/ethers
              , but this is not official.
              The  format of the file is simple; it only contains
              ASCII text lines with a hostname,  and  a  hardware
              address separated by whitespace.

       In  all  places where a hostname is expected, one can also
       enter an IP address in dotted-decimal notation.

FILES

       /proc/net/arp,
       /etc/ethers

AUTHOR

       Fred N. van Kempen, <waltje@uwalt.nl.mugnet.org>